MULTIPLE DENDROCHRONOLOGICAL RESPONSES TO THE ERUPTION OF CINDER CONE, LASSEN VOLCANIC NATIONAL PARK, CALIFORNIA

Trees growing around Cinder Cone, a small basaltic cinder cone in Lassen Volcanic National Park, northeastern California, were investigated for multiple dendrochronological changes, including tree-ring chemistry. Cinder Cone is thought to have erupted in the mid- to late-1600s based on ring-width evidence, but interpreting ring-width changes alone is not straightforward because other types of forest disturbance can cause similar changes. Old Jeffrey pines growing in Cinder Cone tephra as well as away from Cinder Cone itself were core sampled. Ring width and ring element content were measured. “Tephra trees” (trees growing within Cinder Cone tephra) show ring-width changes at AD 1666, but this ring-width signal is not unambiguous for dating the eruption. “Tephra trees” also show changes in ring phosphorus, sulfur, and sodium at AD 1666, but inter-tree variability in dendrochemical signals also makes dating the eruption difficult based on ring chemistry alone. The combination of dendrochemistry and ring-width analysis improves confidence in dating the eruption of Cinder Cone over the analysis of just one line of evidence. This study is similar to a previous case study using dendrochronology at Volcán Parícutin, Michoacán, Mexico, a cinder cone that erupted beginning in 1943. In both cases, dendrochemistry was useful for confirming the dating of the eruptions. When combined with ring-width analysis, dendrochemistry can be useful for improving the precision of dating of cinder-cone eruptions. Based on multiple dendrochronological responses, the eruption of Cinder Cone, Lassen Volcanic National Park, California, is confirmed to AD 1666.